*{
    padding: 0;
    margin: 0;
    box-sizing: border-box；
}
a{
    text-decoration: none;
}
.box{
    width: 500px;
    margin: auto;
    border:1px #000 solid;
}
ul{
    display: flex;
}
ul li{
    list-style: none;
    padding: 10px;
    width: 100px;
    display: inline-block;
    text-align: center;
    cursor: pointer;
}
.nav .active{

    border-bottom: 2px #ff4400 solid;
}
/*.nav li:hover{
     border-bottom: 2px #ff4400 solid;
}*/
.content{
    padding: 20px;
}
.content > div{
    display: none;
}
.content > div.active{
    display: block;
}
.content p{
    line-height: 37px;
}
.content a:hover{
    color: #ff5000;
}